Hi Adam,
(2014/06/14 6:18), Adam Buchbinder wrote:
> When running with UndefinedBehaviorSanitizer, the tests produce the following
> error:
>
> radix-tree.c:836:30: runtime error: shift exponent 18446744073709551613
> is too large for 64-bit type 'unsigned long'
>
> (That's a negative shift exponent represented as an unsigned long.)
>
> Even though the value is discarded in those cases, it's still undefined
> behavior; see the C99 standard, section 6.5.7, paragraph three: "If the
> value of the right operand is negative [...] the behavior is undefined."
>
> Signed-off-by: Adam Buchbinder <abuchbinder@xxxxxxxxxx>
It looks good to me.
Reviewed-by: Satoru Takeuchi <takeuchi_satoru@xxxxxxxxxxxxxx>
Thanks,
Satoru
> ---
> radix-tree.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/radix-tree.c b/radix-tree.c
> index 4f295fc..7457944 100644
> --- a/radix-tree.c
> +++ b/radix-tree.c
> @@ -833,10 +833,10 @@ int radix_tree_tagged(struct radix_tree_root *root, unsigned int tag)
> static unsigned long __maxindex(unsigned int height)
> {
> unsigned int tmp = height * RADIX_TREE_MAP_SHIFT;
> - unsigned long index = (~0UL >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
> + unsigned long index = ~0UL;
>
> - if (tmp >= RADIX_TREE_INDEX_BITS)
> - index = ~0UL;
> + if (tmp < RADIX_TREE_INDEX_BITS)
> + index = (index >> (RADIX_TREE_INDEX_BITS - tmp - 1)) >> 1;
> return index;
> }
>
>
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